I created a guide of how to restore the songs for Steam copies by using the Steam Console. It includes images showing the steps just in case.
This process will download the depots (game versions) from Update 8 for IV and Update 3 for EFLC.
You can take a look at it here: https://steamcommuni.../?id=1376341001
NOTE: This is the "legal way", because sharing game files is against Rockstar EULA (and iirc, GTAF also).